Flowers of some chrysanthemum species include a relatively small, but commercially extractable, amount of volatile oils with insecticidal properties. These oils include the pyrethrins. Only a portion of the flower (in the disk) includes extractable pyrethrins, so inclusion of stem and leaf plant parts during harvesting is typically undesirable. Also, the amount of pyrethrins contained in the flower disk reaches a maximum during a relatively short period of time.
Attempts have been made to harvest pyrethrum flowers mechanically. U.S. Pat. Nos. 4,597,252, issued Jul. 1, 1986, inventor Williames, and 4,761,942, issued Aug. 9, 1988, inventor Williames, describe pyrethrum flower mechanical harvesters. These have not found commercial success due to unacceptably large amounts of the undesired stem and flower plant portions being included during use, and relatively low amounts of mature flowers are harvested from the total available flowers. Thus, substantially all of the world's harvest is presently being picked by hand.